Study of Physicochemical Characteristics of Niobium-Containing Oxide Materials. Part 1. Thermodynamic Simulation

The paper provides brief information about the state of production and use of niobium in steelmaking and about niobium deposits in Russia. Pyrochlore-apatite ores contain a significant amount of phosphorus; therefore, the schemes of their enrichment include a dephosphorization stage, which reduces the niobium extraction into the product, increasing its cost. The possibility of improving the through production scheme, including the enrichment of ores and the smelting of niobium ferroalloy, is shown. The smelting process and the physicochemical characteristics of the used concentrates of the CaO– SiO 2 –MgO–Al 2 O 3 –TiO 2 –Nb 2 O 5 –Fe 2 O 3 –P 2 O 5 system have not been sufficiently studied; therefore, thermodynamic simulation of carbothermal and metal-thermal processes of reducing the oxide system components was performed in order to determine the influence of chemical composition of the system, the amount of reducing agent and temperature on the reduction degree of elements, the composition of the metal and oxide phases, and the metal dephosphorization. Thermodynamic simulation was carried out for temperatures of 1400–1700 °C at a reducing agent consumption of 80, 100 and 120% of the stoichiometrically required amount for the reduction of the system leading elements. With the carbothermal method, the phosphorus reduction occurs quite completely at more than 100% of carbon of the stoichiometrically required amount already at 1100°C and above. With the silicothermal method, the influence of temperature and silicon amount on the reduction degree of Nb, P, Ti and the chemical and phase compositions of the alloy is shown.